Nanoparticle optical properties: Effect of separation distance on near field and far field of a pair of gold spherical nanoparticles

In this present work, taking full advantage of MNPBEM toolbox, the optical properties of gold dimers have been simulated with an emphasis on the extinction spectra. The plasmon resonance wavelength of coupled gold nanospheres as a function of interparticle distance has been studied by varying the surface-to-surface distance from 100 nm to 500 nm. Two distinct regimes are determined namely near-field and far-field, which depend on the distance between the gold dimers and also on the orientation of the nanoparticle pair with respect to the polarization axis of the incident light. When the incident light is polarized along the dimer axis, the wavelength corresponding to the maximum extinction first blueshifts with increasing gap, and then red-shifts as the particle separation are further increased. However, for the perpendicularly polarized excitation, the increase in the separation distance leads to non-monotonic shift in the plasmon resonance wavelength. From this observation, it reveals that the far-field interaction as well as the retardation effect for large particles cannot be ignored as it leads to the damping of the plasmon oscillation, with more obvious effect being associated with perpendicular polarization.In this present work, taking full advantage of MNPBEM toolbox, the optical properties of gold dimers have been simulated with an emphasis on the extinction spectra. The plasmon resonance wavelength of coupled gold nanospheres as a function of interparticle distance has been studied by varying the surface-to-surface distance from 100 nm to 500 nm. Two distinct regimes are determined namely near-field and far-field, which depend on the distance between the gold dimers and also on the orientation of the nanoparticle pair with respect to the polarization axis of the incident light. When the incident light is polarized along the dimer axis, the wavelength corresponding to the maximum extinction first blueshifts with increasing gap, and then red-shifts as the particle separation are further increased. However, for the perpendicularly polarized excitation, the increase in the separation distance leads to non-monotonic shift in the plasmon resonance wavelength. From this observation, it reveals that the far-field...